Muscle can't mobilize fat as quickly as it can glycogen.

There were no differences between diets in muscle glycogen storage over 24 h between equi-Caloric diets of carbohydrate alone (approx 10 grams of CHOper kg body wt per 24 hours and a mixed diet of CHO/Pro/fat.

In recent years, post-exercise nutrition has evolved as an imperative part of training regimens among athletic populations. Athletes of all ages, abilities, and skill levels are adopting some form of post-exercise nutrition to improve performance and enhance the body’s recovery processes following exercise. Athletes in particular are highly susceptible to the detriments of heavy training regimens, because they are constantly depleting their energy substrates and stressing skeletal muscle tissues simultaneously. The macronutrients that have drawn much attention, in reference to the recovery phase of exercise, are protein and carbohydrates. Protein and carbohydrates have their own distinct functions, yet both work to generate an anabolic state within the body when ingested after the completion of an exercise bout. It is necessary for individuals who seek to gain lean muscle mass to induce a positive protein turnover as often as possible. It has been confirmed that protein and/or amino acid ingestion is required to reach a positive protein/nitrogen balance (Borsheim et al., ; Koopman et al., ; Tipton et al., ), and carbohydrate ingestion alone provides marginal benefits on protein synthesis rates (Roy, ). Carbohydrate intake during recovery has been shown to replenish depleted glycogen after intense or exhaustive exercise (Ivy et al., ; Ivy et al., ; Reed et al., ). The addition of protein can further enhance this process (Ivy, et al., ), but only in situations when an inadequate amount of carbohydrate is made available in the diet (van Loon et al., ). A lack of glycogen stores in the muscle and liver will limit the performance capacities of the body during prolonged or higher intensity bouts of exercise (Coyle et al., ). The provided evidence clearly denotes the importance these two macronutrients have in regards to post-exercise nutrition and anabolism. Therefore, the purpose of this review is to discuss the impact of dietary protein and carbohydrate intake during the recovery state on muscle protein synthesis and glycogen synthesis.

Glycogen branching enzyme

N2 - The enzymes Akt, mTOR, p70S6K, rpS6, GSK3, and glycogen synthase interact in the control of protein and/or glycogen synthesis in skeletal muscle, and each has been found to respond to exercise and nutrient supplementation. In the present study, we tested the hypothesis that nutrient supplementation post exercise, in the form of a carbohydrate-protein (CHO-PRO) supplement, would alter the phosphorylation state of these enzymes in a manner that should increase muscle protein and glycogen synthesis above that produced by exercise alone. After a 45 min cycling session followed by sprints and again 15 min later, the subjects (n = 8) ingested 400 ml of a CHO-PRO drink (7.8% dextrose and 1.8% protein-electrolyte) or a placebo drink, as assigned using a randomized, counter-balanced design with repeated measures. Biopsies of the vastus lateralis were taken before exercise and at 45 min of recovery. At 45 min after supplementation, CHO-PRO treatment yielded greater phosphorylation of Akt (65%), mTOR (86%), rpS6 (85-fold), and GSK3α/β (57%) than pre-exercise levels (p

Recent

Thermodynamics of Glycogen Metabolism

The intervention of dietary protein or amino acid supplementation in conjunction with resistance training has proven to effectively increase protein synthesis rates. An original investigation in this area of research (Biolo et al., ) evaluated the effects of intravenous infusion of amino acids (alanine, phenylalanine, leucine, and lysine) at rest and following a lower extremity resistance exercise bout. Their findings revealed a 291% increase in protein synthesis following the exercise bout, while protein degradation remained unchanged from baseline quantities, a response most largely influenced from the 30% - 100% increase in amino acid transport to the active muscle tissue following exercise. Similar protocols in the elderly resulted in augmented rates of protein synthesis accompanied with unchanged rates in muscle protein breakdown which generated a positive protein balance (Volpi et al., ). The practicality, however, for these study designs comes into question due to difficulties associated with intravenous infusion of amino acids after resistance training. Therefore, other researchers have assessed the efficiency of oral administration of amino acids and protein following resistance training. Borsheim and colleagues () found that 3g of EAA ingested one and two hours following a resistance training bout increased protein balance in a similar fashion. Furthermore, it has been established that post-exercise EAA supplementation stimulates protein synthesis, in conjunction with a positive protein balance, comparable to that of intravenous infusion of amino acids (Tipton et al., ), and non-EAA are not necessary to achieve post-exercise anabolism (Borsheim et al., ; Tipton et al., ). Esmarck and colleagues () investigated the effectiveness of an oral supplement containing 10g of protein, 7g of carbohydrates, and 3g of fat when taken immediately after or two hours following resistance training on muscle hypertrophy and strength in thirteen elderly men. The cross-sectional area of the vastus lateralis following twelve weeks of resistance training increased when subjects ingested the post-workout supplement immediately upon completion of all training sessions, whereas when taken two hours after completion, no changes in muscle cross-sectional area were observed. In this study, it was not necessary to measure protein synthesis levels, since the increase in muscle cross-sectional area (hypertrophy) is indicative of a net positive protein balance. Also, these conclusions give insight on the possible time course for consuming post-exercise protein and/or amino acids, as hypertrophy resulted only when protein was immediately ingested upon cessation of resistance training. A more recent study (Tipton et al., ) explored the acute protein balance after exercise when two different proteins were consumed following resistance training. Twenty three non-resistance trained subjects ingested a placebo, 20g of whey, or 20g of casein one hour after completing ten sets of eight repetitions of leg extensions at 80% of their respective one-repetition maximums. Casein and whey protein ingestion yielded similar values of net positive protein balance, and thus an overall increase in protein synthesis (see ). A later analysis revealed that soy protein increased protein synthesis in rats similar to that of whey after a treadmill exercise protocol (Anthony et al., ). A human trial, however, concluded that milk proteins (caseins and whey) in comparison to soy promoted greater muscle protein accretion when they were ingested after regular resistance training (Wilkinson et al., ); a response linked closely to their known impacts on splanchnic and peripheral metabolism, respectively (Fouillet et al., ). Whey hydrolysate ingested after a resistance exercise bout acutely stimulated mixed muscle protein synthesis 31% greater than soy (Tang, et al., ), and post-exercise ingestion of fat-free milk significantly increased lean body mass to a greater extent than soy protein after 12 weeks of resistance training (Hartman et al., ). In addition, protein plus amino acid supplementation can up-regulate muscle protein synthesis in conjunction with resistance training (Willoughby et al., ), but it seems unnecessary to combine protein and amino acids in an attempt to further stimulate muscle protein synthesis if an adequate amount of protein (20 g) is ingested (Tipton et al., ) immediately before or after a resistance exercise bout (Tipton et al., ).

But the muscles contain glycogen.

Fats are more important in slower, enduranceevents and protein is not an energy source although necessary to maintain and repair muscle cells andconnective tissue.The "bonk" occurs when the body's stores of glycogen in the liver and muscles are depletedand the exercising muscle is required to shift to less effective fat metabolism as its primaryenergy source.

Glycogen branching enzyme

The purpose of this review was to discuss the impact of dietary protein and carbohydrate intake during the recovery state on anabolic markers such as muscle protein synthesis and glycogen synthesis. The anabolic processes of muscle protein synthesis and glycogen synthesis are affected by many different variables. Resistance training alone is not potent enough to stimulate a positive protein balance where protein synthesis exceeds protein degradation. The supplementation of protein and/or amino acids following a resistance training bout results in a net positive protein balance that enables skeletal muscle hypertrophy to take place. Carbohydrates play a limited role in protein synthesis, and thus are probably not necessary to prompt hypertrophy training effects. However, carbohydrates are vital to replenish glycogen stores diminished from prolonged or high intensity exercise. Past research has clearly defined that timing of ingestion, GI value of the food, amount ingested, and nutrient composition of the food are all important factors in determining the effectiveness of glycogen synthesis rates. Future research is needed to elucidate the equivocal findings surrounding the combination of protein and carbohydrate supplementation in reference to glycogen synthesis after exercise.

Reviews

“ The addition of protein to carbohydrate consumption in the post-exercise period has led to mixed results. Zawadzki and colleagues () investigated the effects of carbohydrate, protein, and carbohydrate plus protein supplements on muscle glycogen synthesis after two hours of cycling. Participants ingested either 112g of carbohydrates, 41 grams of protein, or 112 grams of carbohydrate and 41 grams of protein immediately, and two hours after three separate exercise bouts. Supplementing carbohydrates and protein together resulted in higher glycogen stores than the carbohydrate and protein groups. Original research in this area concluded that the increase in glycogen synthesis is directly related to the upregulatory effect that certain amino acids have on insulin (Floyd et al., ; Knopf et al., ). Therefore, it is reasonable to believe that carbohydrate plus protein intake following exhaustive exercise will further enhance glycogen synthesis over carbohydrates alone. On the contrary, the study design of Zawadzki limits the generalization of the findings due to the variation in caloric values provided to the treatment groups. Glycogen stores may have been further replenished in the carbohydrate + protein group, because additional calories were consumed. A more recent study took a second look at the possible impact of protein + carbohydrate supplement on glycogen synthesis when compared to a carbohydrate solutions of equal caloric value and equal carbohydrate content (Ivy, et al., ). Cyclists completed two hours of exercise on three different occasions to analyze all treatments. Supplements were ingested immediately and two hours following exercise. Four hours after the completion of the exercise bout, 47% of glycogen depleted during exercise bout was restored in the carbohydrate + protein group. The equal caloric value and carbohydrate content groups experienced 31% and 28% glycogen restorations respectively. The conclusions of the Ivy study help to support the inferences made earlier by Zawadzki and colleagues. It is apparent that protein can further augment glycogen synthesis when ingested with an adequate amount of carbohydrates. However, conflicting evidence does exist. van Loon and colleagues () concluded that the ingestion of ample carbohydrates is the limiting factor in determining the magnitude of glycogen synthesis after exercise. When protein was added to a sufficient carbohydrate solution, glycogen synthesis was not further stimulated. Other investigations have seen enhanced rates of glycogen synthesis during the post-exercise period (Berardi et al., ; Bowtell et al., ; Tarnopolsky, et al., ) whereas others disagree (Carrithers et al., ; Jentjens, et al., ; Yaspelkis and Ivy, ). In conclusion, it looks as if glycogen synthesis can increase with the addition of protein under certain circumstances, although some evidence lacks in supporting this claim. A summary of factors affecting glycogen synthesis immediately after exercise are displayed in . ”

Regulation of GlycogenMetabolism

The liver can store excess glucose as glycogen.

Gallery Glycogen Storage Disease

Glycogen Biosynthesis; Glycogen Breakdown - Oregon …

If the body is low in glucose and glycogen, cortisol will send amino acids to the liver to make new glucose, referred to as gluconeogeneses.

This group of studies has given insight on several important components related to anabolism in the post-exercise state. Carbohydrates alone seem to have a minimal effect on the net protein balance following exercise. Whether they marginally reduce protein degradation or slightly increase protein synthesis, carbohydrates unaccompanied by protein are unable to generate a positive protein balance and stimulate skeletal muscle hypertrophy. Different forms, sources and/or quantities of protein supplemented with carbohydrates can interact to create a greater anabolic environment in the post-exercise state by elevating protein synthesis levels far greater than carbohydrates alone could initiate. If a positive protein balance and subsequently muscle hypertrophy is desired, protein must be added to carbohydrate supplementation in order to fuel these processes. The combined effects of carbohydrate and amino acid/protein supplementation on protein synthesis are equivalent to their independent effects (Miller et al., ).